Lock washer



Patented July 14, 1942 LOCK WASHER llohn L. Koubek, Anderson, Ind., assignor to @General Motors' Corporation, Detroit, Mich., a cori poration of Delaware Application June IZ, 1939, Serial No. 278,670

(Cl. ISI-14) 1 Claim.

This invention has to do with a lock washer adapted to encircle the shank of a bolt and prevent its withdrawal much the same as the usual nut does except that my improved lock washer is provided with teeth which are forced into bit-- ing engagement with the shank of the bolt so that in order to remove the bolt it is necessary either to cut through the Washer or to pry on the washer and in doing so force the washer teeth to cut channels extending to the end of the bolt. In order that the washer teeth may cut into the metal of the bolt rather than bend, it is necessary that the washer be of hardened metal. The teeth should, of course, be relatively sharp To further insure against removal of the bolt it will often prove advantageous to provide a countersink in the support or in a nut -against which the washer abuts, the countersink housing the washer so that it is difcult, if not irnpossible, to pry the washer loose from the bolt.

In the drawing: Figure 1 is a view partly in section showing the improved lock washer in use to secure a fog lamp to the usual bumper bar of an automobile.

Figure 2 is an enlarged view, partly ,inl section, taken on line 2-2 of Figure 1.

Figure 3 is a view of the washer before it is formed.l

ventional. In the present instance the nut 30 l' not only serves to draw the parts togetherto cause the clamp 22 and cooperating clamp 32 to grip the bumper bar I6 but at the same time causes the washer III to be flattened out into the shape shown in Figure 2 with the teeth I8 embedded in the shank of the bolt. Once distorted to the shape shown in Figure 2 the washer I0 remains permanently in that shape and the only way to get it off and release the bolt is to either cut through the washer and expand it or else pry the Washer off or drive the bolt through it and either of these last methods requires that the teeth 8 cut themselves channels extending lengthwise of the bolt to and through the free end thereof. This, of course, requires the use of considerable force and the resulting no'i'se or the noise incident to cutting through the washer, bolt shank or other parts is such as to deter theives Figure 4 is a perspective view of the washer.

Figure 5 is a view of the parts shown in Figure 2 prior to attening the washer.

Figure 6 is a view showing a slightly modified form of washer.

lIn Figure 1 the improved washer I0 is shown as it is used in securing a fog lamp I2 to a bracket I4 and also in securing the bracket I4.to bumper bar I6 so as to prevent theft.

The washer, as shown in Figures 3 and 4, consists of an annular sheet metal stamping having its inner periphery scalloped to provide pointed tongues I8. these tongues preferably being sheared to provide substantially triangular surfaces 2Il at their tips extending parallel to the axis of the washer so as to permit the washer to be readily slipped over the shank of the bolt,

In Figures 2 and 5, 22 indicates apart through which the shank Aof the bolt is passed. -In.the

case illustrated this is a clamp which slides on the bolt shank and engages the lower edge of the bumper bar I6. 24 indicates a countersink provided in the part 22 to receive the washer III. 26 indicates a plain washer lsurrounding the shank beneath `the lock washer III. 28 indicates the conventional spring lock washer, and 30 the securing nut. 'Ifh parts 26, 28 and 30 are con- 55 from attempting to remove the article secured by the bolt.

` The washer may be made of any suitable metal,

such as sheet steel and may be hardened by any known methods such, forexample, as cyanide treatment. l

In Figure 6 there is shown a slight modication in that the scallops at the inner edge ofthe washer are longer, providing teeth of greater width.

Iclaim:

In a theft proof locking means for securing bolts the combination of a support having an -aperture therein, a countersink around the aperture, a threaded bolt extending through the aperture, a lock washer made of hardened sheet metal and formed into substantially the shape of a continuous unbroken frustum of a cone except that the inner edge of the washer is interrupted to form projecting teeth the ends of which are bounded by surfaces extending parallel to the axis of the washer, the aperture deflned by said surfaces being of slightly greater diameter than the said bolt to permit the washer to be readily' slipped over the bolt with its inner periphery seated in said countersink, said Washer being sufciently thin and deformable so that when clamped in place by tightening lanut on the bolt it will be lstressed beyond its elasticlimit and will be attened out between the nut and the support so as to lie wholly within the said countersink and the teeth will bite into and deform the shank of the bolt thereby preventing removal of the bolt except by stripping its threads or otherwisedestroying the bolt or washer.

1 l JOHN L. KOUBEK. 

